Add ia64 patch.

[linux-flexiantxendom0-3.2.10.git] / kernel / timer.c

diff --git a/kernel/timer.c b/kernel/timer.c
index caa3771..6ffa0bf 100644 (file)
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -451,6 +451,7 @@ unsigned long tick_nsec = TICK_NSEC(TICK_USEC);     /* USER_HZ period (nsec) */
  */
 struct timespec xtime __attribute__ ((aligned (16)));
 struct timespec wall_to_monotonic __attribute__ ((aligned (16)));
+unsigned long last_nsec_offset;
 
 /* Don't completely fail for HZ > 500.  */
 int tickadj = 500/HZ ? : 1;            /* microsecs */
@@ -605,7 +606,7 @@ static void second_overflow(void)
 /* in the NTP reference this is called "hardclock()" */
 static void update_wall_time_one_tick(void)
 {
-       long time_adjust_step;
+       long time_adjust_step, delta_nsec;
 
        if ( (time_adjust_step = time_adjust) != 0 ) {
            /* We are doing an adjtime thing. 
@@ -621,11 +622,11 @@ static void update_wall_time_one_tick(void)
                time_adjust_step = tickadj;
             else if (time_adjust < -tickadj)
                time_adjust_step = -tickadj;
-            
+
            /* Reduce by this step the amount of time left  */
            time_adjust -= time_adjust_step;
        }
-       xtime.tv_nsec += tick_nsec + time_adjust_step * 1000;
+       delta_nsec = tick_nsec + time_adjust_step * 1000;
        /*
         * Advance the phase, once it gets to one microsecond, then
         * advance the tick more.
@@ -634,13 +635,33 @@ static void update_wall_time_one_tick(void)
        if (time_phase <= -FINEUSEC) {
                long ltemp = -time_phase >> (SHIFT_SCALE - 10);
                time_phase += ltemp << (SHIFT_SCALE - 10);
-               xtime.tv_nsec -= ltemp;
+               delta_nsec -= ltemp;
        }
        else if (time_phase >= FINEUSEC) {
                long ltemp = time_phase >> (SHIFT_SCALE - 10);
                time_phase -= ltemp << (SHIFT_SCALE - 10);
-               xtime.tv_nsec += ltemp;
+               delta_nsec += ltemp;
+       }
+       xtime.tv_nsec += delta_nsec;
+
+       /*
+        * The whole point of last_nsec_offset is that it can be updated atomically and
+        * lock-free.  Thus, arches that don't have __HAVE_ARCH_CMPXCHG probably can't use
+        * last_nsec_offset anyhow... --davidm 2003-Feb-11
+        */
+#ifdef __HAVE_ARCH_CMPXCHG
+       if (last_nsec_offset > 0) {
+               unsigned long new, old;
+
+               do {
+                       old = last_nsec_offset;
+                       if (old > delta_nsec)
+                               new = old - delta_nsec;
+                       else
+                               new = 0;
+               } while (cmpxchg(&last_nsec_offset, old, new) != old);
        }
+#endif
 }
 
 /*
@@ -777,7 +798,6 @@ unsigned long wall_jiffies = INITIAL_JIFFIES;
 #ifndef ARCH_HAVE_XTIME_LOCK
 seqlock_t xtime_lock __cacheline_aligned_in_smp = SEQLOCK_UNLOCKED;
 #endif
-unsigned long last_time_offset;
 
 /*
  * This function runs timers and the timer-tq in bottom half context.
@@ -811,7 +831,6 @@ static inline void update_times(void)
                wall_jiffies += ticks;
                update_wall_time(ticks);
        }
-       last_time_offset = 0;
        calc_load(ticks);
 }